Tennis ball



NOV. 9, 1948. L, s. M. LEJEU NE I 2,453343 TENN I S BALL Filed Nov. 24, 1941 5 Sheets-Sheet 1 Nov. 9, 1948. s. M. LEJEUNE 'mums BALL 5 vSheets-Sheei'. 2

Filed Nov. 24,- 1941 Sw, k.

L. s. M. LEJEUNE I 2,453,143

Nov. 9, 1948.

TENNIS BALL Filed Nov. 24, 21941 5 Sheets-Sheet 3 f laane.,

i l'lygp Nov. 9, 1948. L. s. M. LEJEUNE: 2,4537143 TENNIS BALL Filed Nov. 24, 1941 s sneets-s'heet 4 J moy'eune-J) Nov. 9, 1948. ..s. M. LEJEUNE'. 2,453J43 TENNIS BALL Filed Nov. 24, 194-1. 5 sheets-sneet 5 Patentecl Nov. 9, 1948 TENNIS BALL Leon Sylvain Max Lejeune, Paris, France; vested in the Attorney General of the United States Application November 24, 1941, Serial No. 420,292 In France August 9, 1938 3 Claims.

The present application relates to tennis balls and is a continuation-in-part of my prior application, Serial No. 250,617, filed on January 12, 1939 (abandoned).

The invention concerns a tennis ball complying with the conditions prescribed by the International Lawn-Tennis Federation as regards the balls used in international lawn-tennls matches, i. e. the conditions which define the maximum and minimum limits of the diameter of the ball, its Weight, its height of rebound for a given height of fall, and its degree of compression under a predeterminated stress applied during a given eriod of time.

The invention has also for its primary object the provision of a tennis ball of the character indicated which is not subject to losing its inner pressure after a more or less long lapse of time.

Another object of the invention is to provide a tennis ball which practically does not wear out.

Still another object of the invention is to provide a tennis ball the initial launching velocity of which can be very high and remain the same during the whole life of the ball.

A further object of the invention is to provide a tennis ball upon which the ground produces no damping or deadening effect (such as that which is observed with the usual felt-covered tennis balls), so that the rise of the ball from the ground to the receiving racket can accordingly be very rapid.

A still further object of the invention isito provide a tennis ball which is not sensitive either to cold or to heat or to moisture whereby the playing characteristics of the ball remain the same regardless of atmospheric conditions.

A further object of the invention is to provide a tennis ball which can be Washed.

The tennis ball according to the invention comprises a body filled with air substantially at atmospheric pressure, this body being formed of two hemispherical calottes united by vulcanized rubber, each of which is made of a uniform fabric impregnated with vulcanized rubber so as to form a homogeneous mass of textile elements lmpregnated throughout and firmly united by means of vulcanized rubber.

The fabric which is used for forming the hemispherical calcttes can be composcd of vegetable or animal fibres or threads' As above mentioned, this fabric must be a uniform fabric, i. e. a fabric in which the Composition of the threads as well. as their tension and degree of twisting are the same for the Warp and the weft, so that the fabric has substantially equal tensile strength in all directions. Such a fabric can be made by having uniform weft and Warp threads subjected to the same tension, or, if these conditions are not complied with, by superposing two or more layers of a fabric which are so arranged that the unevennesses of their weaving are mutually compensated. To this effect it is possible, for example, to use to advantage a cotton melton formed of a very fine and twisted Warp and of a thick and very slightly twisted weft-or an equivalent fabric-and to superpose two pieces of such a melton so that the weft threads of the one are at 96' with respect to those of the other. Such a unit can be impregnated with rubber in a uniform manner and its elasticity is the same in all directions. I

The body of the ball formed in the above mentioned manner is advantageously covered inwardly and outwardly with an impervious layer of vulcanized rubber and it is furthermore covered with a layer of canvas on the outer surface to which a layer of rubber, also vulcanized, is applied. This latter layer of rubber, whichforms the outer surface of the ball, is provided with relief patterns adapted for regulating the velocity of the ball and ensuring the regularitybf the direction it takes in the air.

In order to make a tennis ball according to the invention, one preferably proceeds in the following manner:

Cotton melton having a weight of preferably 450 to 500 grams per square meter is first treated so as to facilitate its impregnation with rubber,

for example by dipping it in water to which aV "wetting" agent has been added. The prepared melton is then impregnated with rubber latex by being passed through a bath of concentrated latex, for example a latex containing 50% of rubber, the said bath containing the vulcanizing products, accelerators and other products usually covered therewith.

alicante used in the rubber industry. The fabric thus impregnatcd is then freed, by light pressure, from the excess latex which it may have absorbed, and is coagulated, for instance by passing it through a bath of dilu'ted acetic acid, and then, after having been freed from an excess of the coagulating bath, for instance by light pressure, it is cut into pieces or discs after which two of the impregnated pieces or discs are laid one upon the other so as to obtain a uniform textile unit. This operation is carried out, preferably, by first laying one of the piec'supori the other with'their Warp threads arranged at 90 and then pressing them one upon the other so as to cause them to adhere, by expelling a part of the coagulating bath remain-ing in the melton, after which the desired discs are cut out of the resultant material.

After washing with water during a sufiiciently long time to eliminate the excess acid as well as the other substances soluble in water remaining in the discs, the latter are pressed into the shape of a hemispherical caiotte. This operation is preferably efiected by putting one of these discs of impregnated, double layer melton into a cylindro-'hemispl'ierical die the rim of which is formed by an annular ring embedded in the die and by stampirig the disc by means of a cylindre-hemispherical punch which leaves between the die and the'said punch a space corresponding approximately to the final thickness which the hemisphericalcalotte must have. The die can advantag'eo'usly be provided with grooves or holes which permit of the escape of a certain amount of the water which is exuded from the discs under the action of the stamping pressure.

The punch and the die are then separated one froml the other, leaving the calotte on the punch With; surrounding it at its base, the annular ring material rwhich remains about the base of the` calotte is cut away so as to give the calotte its exact hemispherical shape, the edge of the calotte terminating in' a diametral sectional plane. This calotte is then dipped into a bath of rubber solution sothat the entire surface of the calotte is As soon as the solution is dry, two of these calottes are united together to forml a sphere by bringing their diametral sectionalfplanes into contact, after having introducedinto one of these calottes a predetermined amount by weight of a Chemical Compound capablel of decomposing under the action of heat and emitting a gas, while leaving a minimum amount of ;solid residue. This Chemical may be, for example,fcarbonate of ammoniac which decornposes at aV temperature of about 80 C. The quantity of this compo-und introduced will be such that during its decomposition under the action of aV rise in temperature such as has just been indicated, a high pressure of the order, for instance, of 2 to 3 kilogsper square centimeter, is created in the sphere formed by the assembly of the two calottes.

IAfter Shaping the sphere containing the substance utilized for the purpose of giving off gas under the action of heat, a strip of gum may be applied onto the joint of the two hemispherical calottes. The width, the thickness and the length of this strip are so determined that a previously fixed weight is obtained for the so formed ro'ughed-out ball. This roughed-out ball is then covered with pieces of canvas impregnated with rubber, cut out in such a manner that when joined edge to edge they completely cover the entire surface of the sphere. This will be obtained, for instance, by means of two pieces of canvas each of which has the form of a lemnis- Ynilar to the form of the two pieces of felt L1 cover tennis balls as usually made. Each roughed-out and canvas covered ball is then placed into a spherical mould preferably formed two parts applied one against another, this mculd being provided with a small hole to allow the outside of the die to communicate vwith the inside. If'the ball must be provided onlits outside surface with projections or hollows, the die is provided, on inn-er surface, with hollows or projections forming the counterpart of the configuration which the outer surface of the ball must finally have. Eventualiy, in order to obtain a better nal appearance of the ball and also to obtain an indelible marlring of the same, the inward portion of the opening of the hole with which the die is provided will be provided with al protection, for instance a circular projection which, accordingi', will produce in counterpart a hollow in the ball.

The mculd containing the roughed--out ball-is then placed into a vulcanizatio-n autoclave Where it is brought to the desired temperature: for" the period necessary for the vulcanization of the-rubber components of the ball, this temperature in every case, sufiiciently high for ensuring 'the decompositicn of the gas-pro-ducing chemical conioound in the inside of the ball. The resultant evolution of gas within the ball presses the spherical wall of the ball against thev die, and eventuaily gives rise to the formation of 'projectio'ns or hollows on the outer surface ofV the ball. This vuicanization ensures a thoroughunion of the different elements and ingredients forming the wall of the ball and homogenizes in a certain measure the mass which forms this wall.

As soon as the vulcanization is completed, a. ne-edle is introduced into the hole of'the mould ball is perforated in order to permit the gases contained in the ball to escape and consequently to allow the inner pressure of the ball to balance with' the outer pressure. For'thisfpurpose the perforatingineedle is preferably. hollow'and made in. the form of a trocar. As' soon as this balance of pressures is obtained, the mould is opened and the ball removed, after which the hole in the ball is sealed. riChis is advantageously effected by introducing into this hole a rubber thread coated with a rubber solution which thread is cut at the outer surface of the wall of th'eball, if the mould is smooth at this place, or'at the level of the bottom of the small circular cavity provided in the outer wall of the ball'if the mould is provided there with the above mentioned pro'- jection. In. this latter case a lozenge of vulcanized rubber coated with a rubb-er'solution is firially placed into the cavity in question.

' To introduce the rubber thread into the 'hole 50 which was made -n the ball in order' to balance the iuner pressure with the pressure ofthe surround ig air, a tool is used which is formed, for

oe, of a punch or a hollow needle into which the rubber thread coated with af rubber solution is inserted, so that the said'thread is Hush with the point of the needle. The so equipped needle is introduced through the-hole the ball into the inside of' the latter, carrying with it the rubber thread. This threadflis then maintained in its position with respecttorthe ball, and the needle is removed unti1 it leaves 4 the wall'ofthe' ball'. Since the rubber thread 'has'remained stationary with respect to the ball itself 'during' this movement, the walls of the hole close again onto the rubber thread. Thus the hole is stopped and the only thing remaining to do is to cut the rubber thread fiush with the outer surface of the ball in one or the other of the above mentioned conditions. This having been done, the above mentioned lozenge is then evenltually' applied and stops the cavity in the outer surface of the ball. Upon drying, the rubber solution which covers the thread unites the latter to the wall-of the ball and thus tightly and definitely closes the hole.

The appen'ded drawing shows by rway of example, on the one hand, a diagram of a plant f adapted for making tennis balls according to the invention and, on the other hand, the ball during various steps of its manufacture.

In this drawing:`

Figure 1 is a view in elevation of the first part of such a plant up to the'coagulation of the latex in the impregnated fabric.

Figure 2 is a similar view showing the subse- '1 quent steps of the manufacture up to the preparation of the pieces of impregnated fabric from which thev discs which serve for making the balls ar'e to be-cut out.

Figure 2A is a perspective schematic view showingthe relative positions of the Warp and weft threads of two adjacent fabric pieces preparatory to forming the latter into a calotte.

'Figure 3 is another similar view of the plant up to and including the operation of making the hernispherical calottes ready for joining to make the balls. I

Figure 4 is, in the same manner, a view in elevationv |of the subsequently used parts of the plant up to the production of calottes ready to be united forproducing the roughed-out balls.

' Figure 5 is a cross' sectional view of the die for themolding of a hemispherical calotte.

Figure 6 is alview of the corresponding punch. 4Figure'? shows the resultfobtained by punch pressinga circular blank by means of the die and punchof Figures 5 and 6.

r -1 Figure 8 is aview in elevation, partially sectional, of the calotte 4mounted on its punch.

Figure 9 is a view, partially sectional and partiallyinelevation, of a-calotte during the drying operation, 4 r

Figure 10 is a view in elevation, partly in sec- K, tion, of a calotte ready for-assembly.

Figure 11 is a view of the roughed-out ball comprising two calottes assembled together with a rubber layer applied over the joint.

for the purpose of inserting the stopping thread in the pressure equalizing hole.

Figure 18 is a sectional view showing the punch i in operation for the' insertion of the stopping tbreadxinthesaidhole.,...

Figure 19 is a similar view showing the sealng thread inserted and the tool removed.

Figure 20 is` also a sectional view of the pressure equalizing hole stopped by the stopping thread with a finishing plug in place.

In the example of the plant shown for making the ball, the said plant comprises a vat in which is placed al stack of cotton melton. In this vat vwhich is filled with Water to which a wetting agent has been added, the melton 2 is impregnated with moisture. It is then carried on by a rotating roll 3 above which is a compressing roll 4 which expels the excess water carried by the melton. Then the melton passes over another driving roll 5 and from there into a vat 6 containing a bath of latex l. After having passed under the rolls such are are indicated at 8, which maintain it under the surface of the latex, the melton passes between a driving roll 9 and a Weighted roll lil which is sufficeintly heavy for expelling the excess latex as well as the air contained in the melton. From there, the melton, carried by the rotating roll l2, passes into a coagulation vat l 3 under rolls such as are indicated at Ul whence, after having been coagulated by conta-ct With a bath of acetic acid [5, the melton is carried forth by a rotating roll Hi onto a table IT where its coagulation is completed. Carried by the sct of rolls lil, it comes in a damp condition onto a table is where it is cut, by means of the cutting press into square pieces 2| of sufliciently large size to permit of subsequently cutting therefrom circular blanke of a suitable size for making hemisph'erical calottes.

The operator then lays two of the pieces of impregnated and -coagulated melton one upon the other so that the Weft and Warp threads of the one are at with respect to the corresponding threads of the other (see Figure 2A). B-y means of a roll he presses these pieces one against the other in order to cause them to stick together and in order to expel the excess of coagulating liquid remaining in the impregnated fabric. The resultant pieces are then Washed with water in a vat 22 whence they are taken and cut into circular discs 23 by means of the cutting press 24.

The discs 23 are then Stamped out into hernisp-herical calottes in the dies 25 by means of punches 26. The cavities in the said dies (see Figure 5) have `as indicated at 21, the shape of the outer surface of the cal-otte to be formed, -and the cavities termina'te at their upper part in an annular groove in which a ring 28 is removably seated. The punch 25 (see Figure 6) has ext-ernally a surface 29 corresponding to the inner surface of the hemispherical calotte lto be formed, an. annular part correspond-ing to that of the ring 218, anda base 39. Figure '7 shows the Stamped lout calot'te Jil the edge of which is clamped between. the ring 28 and the punch 26. When removed from the stamping press 32, thepunch 26 is separated from |the die and carries with it the hemispherical calotte`3! and the ring 23 (see Figure 8). During 65. the stamping operation the liquid and the air which are in excess in the impregnated blank are expelled through passages such. as indicated at 33 in the die.

The formed calotte blank is placed with its punch and its ring on a heating :table 34 for evaporating the water contained in the blank. As soon as the blank -is dry, |the ring 28 is removed and the excess -3ia of material is cut away by means of the press 35 so as to form a calotte 3l,

f the. edge 3-6 of which is -in the diametral plane of .c..the geometrical sphere of which the calotte is a segment (see Figure The'calotte-s l3| 'so f-orrned are then removed from the punch and dipped into a bath -of rubber solution 31 and then -dried in a drying-room 38. After drying, both calottes are united together by their rims 35 after introducing into one of them a certain quantity of carbonate of amnioniac, or other equivalent compound, capable of producing a gas at a temperature which is lower than or equal to the temperature of-vulcanization. Thus a sphere is formed'(see'Figure ll). Over the joint formed by bringing together the rims 3t of the calottes a 'strip of gum 39 is placed, :the thickness, the width and the l-ength being determined so as to produce a -roughed-out |ball of a weight equal to that of the other balls so formed when completed, so that all balls have a weight within the limits fixed by the International Lawn-Tennis Federation regulations.

On the roughed-out ballytwo pieces 40 (see` Figures 12 and 13) of canvas of -uniformtexture are applied which are coated on one of their faces with Vulcaniizable gum, calendered yon the canvas. The shape of each of these pieces -is such,

that, when two of them have been applied onto the ball, they completely cover its surface without overlapping one another, the gum being on the outside. It' is advantageous to give the pieces the shape of a lemniscate in the usual manner.

The canvas covered ball is then placed into a mold (see Fig. 14) formed of two sections 4| and 42 which define a spherical cavity when symme'trically registered. The inner surface of each section of the mould is provided with a series of grooves such as indicated at 43 adapted to p1`0-v ;u.

-duce projections ll'lo. on the outer surface of the finished ball (see Figure 13) capable of producing the same playing effects as the felt which covers the usual balls. In the embodiment shown in the drawing, the said grooves are circular and are shaped as if generated by a substan-tially equilateralv triangle lying in a diame'trical plane of the sphere and the vertices of which move in a series of parallel planes perpendicular with the.plane of the triangle. There are provided in this case three sets of projecti'ons which are at right angles to each other.

One of :the sections of the m-ould is provided with a barrel ilt slightly projecting into the; in-

' terior ofthe section and p-rovided with a passage Elli. The unfinshe-d ball formed by the impregnated calottes 3t covered with pieces'of gummed canvas iii! and coated with a coating 46 of rubber solution is placed into the mould. Then pressure is exerted on the plates 41 and 48 so as :to force the f sections together around the ball. Thetemperature of the mould is then brought to the temperature at which the Vulcanization of the rubber components of the ball takes place. At this temperature, the Chemical compound 49 which.

was introduced into the ball, before the joining of the halves thereof, vaporizes and exerts on the inside of the ball a sufiicient pressure which firmly presses the walls of the ball against the interior of the mould, thereby causing the gum which im-'i pregnates the cover pieces 40 to penetrate into the grooves 653 and to fill them. As soonas the vulcanization has been completed the :ball is perforated by means of a trocar introduced through thepassage rlift, to cause the pressure in the ball to Subside to atmospheric pressure. Then the mould is opened and the Iball removed therefrom. The only thing remaining to do then is to seal the hole 59 in the ball. In the embodiment describedand shown, this is effected by means of a hollow punch obottom of the: reces-s .:55 'which was formedi irl-the fball rby=the barre1.44 of-thedie. Thisrrecessiis filled with a lozenge 56 covered.with a rubbersolution-which covers: the exposed end,r of the sealing .,thread 54, saidflozenge being stuck irl position;

lThus =thread.and' :lozenge are firm-ly uniitedftogthe han. `f

The lozenge 56.1;can be Iof desired` :colour so as to permit 'an identification of.the/:ball-s'.v for example in the coursev of, the game.

kWhiie the ;foregoing specification and'V the appended drawings illustrate. anV embodimentof the invent-i-on,=.,other em-bodiments of tha-inventi-on :cant be| made Without; departing;from-the 's-copelof the invention. Thus, for example,l to, obtain'a uniform fabric by layingoneupon lanotherftwo meltons or equivalent fabrics a.t:-9.0'.-W-ith` respect one-to another, instead of impregnating, theysaid meltons separately las in the-above described ein- `loadirneritbeforeesticking them together, it ;would be possible to apply. them :one-upon;theptherat 30r before the impregnatiomand impregnatethem thereafter.

WhatI claim is: i i I 1. A tennis bell compri-sing a hollow body confining air at substantially atmospheric pressure, said body, being composed of a, pair ofhemisplierical calottes J'oined together, each 4calotte,being shaped out of fabric of uniform linear tensile strengthlin. substantitally all rdirections....-a`njdlimpregnated with rubber, the rubber and thejfabric ;of .the calottes beingtogether moul-ded andfvul- 'canized Ito define the shape :an-d substance of said hollow-body, said hollow body being formed with a perforation closed by a plug. said plugcomprising a, rubber thread secured inJthe perforationan-d a rubber lozenge appliedfionithe outer end'of' the thread.

'2. "A tennis "ballfcomprising-a v-re'silient hollow sphere confining air` under'-'atmosphericv pressure, said sphere comprising a moulded =andvulcanized self-supporting bodyfconsistingofa pairofr 'assembled hemispheri'calHcalottes'resistant to radial deformation to normally assume -a spherical shape, said calottes each individuallyficonsisting-of reinforcement -composed'of two rubber impreg- Vnate'd pieces'of fabric coextensivewith the entire H-wallstructure of the associated calotte, thepie'ces being superimpose-d on each other withthe Warp and weft= threads of one of'the pieces arranged at right| ang-les to: those 4'of the other piece whereby the wall reinforcement has substant-ially equal "lineartensile'strength in all directions. i

3. A tennis ball comprising ai'hollow bodyy confiningair -at -substantially atmospheric i pressure, said body being composed of a pair'of hemispheri- Ical calottes joined together, -each calotte-'b'eing shaped out of fabricof uniform linear 'tens-fie strength in substantially allidireotions fandfimlfpregnatecl ywith rubber, the rubber 'an-d' the fabric of the calottes beingtogcthenmoulded"andivul- '-canize'd to define'the shape -and substance offsaid :hollow-body, said'hollow body -compris'in'gL-a perforation :and an outer recessfcoaxialitherewith,fa

2,4:ss,14a

rubber thread stuok -in the said perforation and a Number plug stuck in the said recess and made even with 1,187,029 the outer perphery of the ball. 1,466,609 2,023,673 LoN sYLvAIN MAX LEJEUNE. 53 450 2,367374 REFIJRENCES CITED 2373399 The following references are of record in the file of this patent:

UNITED sTATEs PATENTS 1 Nulznzke 17 Name Date Winterbauer J un-e 13, 1939 Number Re. 21,115

Name Date Beebout June 13, 1916 Weaver Aug. 28, 1923 Ellis Dec. 10, 1935 Twiss Sept. 8, 1936 Reach Jan. 16, 1945 Lejeune Apr. 17, 1945 FOREIGN PATENTS Country Date Great Britain Sept. 4, 1924 

